Online Desk : In an interim analysis, scientists at icddr,b and the Institute of Epidemiology, Disease Control and Research (IEDCR) with support from the United States Agency for International Development (USAID) measured levels of SARS-CoV-2 IgG antibodies in the blood of 120 participants before vaccination and then at one and two months after vaccination with the first dose of the Covishield™ vaccine, says a press release.

The vaccine recipients were aged between 40-73 years of age (average age of 49 years) comprising of individuals with or without history of prior COVID-19, and from Dhaka city.

It was found that one month after vaccination 92% of the people who received the first dose of vaccine to have high immune response (geometric mean concentration of antibody against the virus 2,586 ng/ml), and 97% of the people to have even higher immune response (GMT 3,460 ng/ml) two months after the first dose of vaccination. Cut-off for a positive IgG antibody response to the spike protein of SARS-CoV-2 was set at 500 ng/ml using 355 serum samples collected prior to the onset of the pandemic.

46 participants (average 48 years) with previous RT-PCR confirmed SARS-CoV-2 infection history (between April 2020 – January 2021) were also included in the analysis. Participants who had a previous infection with SARS-CoV-2 (1 month or earlier before vaccination) showed more robust response after receiving the first dose of vaccine. A fourfold higher magnitude of antibody response was seen among these participants at two months after receiving the first dose vaccine.

Dr Firdausi Qadri, Senior Scientist at icddr,b who is leading the study from icddr,b in the analysis said, "We now know that the Covishield vaccine induces robust immune response in Bangladeshi adults which is indeed a great news. However, we will continue working on evaluating the neutralising ability of the antibody as well as the T and B cell responses. We will also continue assessing the effectiveness of the vaccine in our setting."

Commenting on the importance of the study, Professor Tahmina Shirin, Director, IEDCR said, "Our analysis confirmed that the vaccine works and people should get it when their turn comes. However, everyone should continue wearing face mask and maintain physical distancing along with personal hand hygiene to keep themselves and their loved ones protected from COVID-19."

icddr,b and IEDCR have started a large scale study at 12 sites in eight divisions across Bangladesh that will involve about 6,300 participants who will complete their full course of vaccination. Participants will be followed up for two years in a longitudinal design for assessing antibody responses after vaccination (day 0 and months 1, 2, 3, 6, 12, 18, and 24) to determine the longevity of antibody response.

The first part of the study is funded by the USAID and partially by the Bill and Melinda Gates Foundation. Currently both IEDCR and icddr,b are looking for more funds to complete the study.

The Covishield vaccine is developed by the Oxford University vaccine group, marketed by AstraZeneca and manufactured by Serum Institute of India.